MAX DAX Function giving incorrect sum

Hi,

I have a requirement where I have to multiply an amount by 5 if the current month is the first month of quarter, else multiply by 4. Ex: if the month is January(1), April(4), July(7), October(10) then multiply by 5, else multiply by 4 for the rest of the months.

I have written below DAX formula for it:

This gives proper result in most cases where all the months are either start of the month (any combination of 1, 4, 7 ,10) or the other months (any combination of 2, 3, 5, 6, 8, 9, 11, 12).

But gives incorrect result when the months selected are a combination of start of quarter months and other months (ex: 10 and 11).

Below is the snapshot of the result:

This example should sum to 8,930,815.3 but currently it shows 7,948,491.08.

Kindly advise what can be done to achieve the correct results, or if anything is not right in the applied DAX formula.

Thanks in advance!